In Aotearoa New Zealand, the continuing disparity in educational outcomes has resulted in a growing call for changes in teacher preparation to better support culturally diverse learners in ways that are responsive to the particular national and cultural context. This paper presents findings from practitioner inquiry into a teacher education program specifically designed to address this need within the national context of 'biculturalism', a treaty-based sociopolitical partnership between Maori and Pakeha (nonMaori). Grounded in sociocultural theory, this inquiry examined how the iterative use of a specific 'cultural tool', a synthesizing framework of culturally responsive and sustaining pedagogy, within the program supported 16 secondary teacher candidates to develop their professional identity as culturally responsive and sustaining teachers. Although the tool is program-specific, the findings suggest more generally that use of locally developed cultural tools and frameworks can play a positive role in supporting preservice teachers' identity development.